- Using drugs which ineligible combination with valproic acid, including mefloquine, St.-John's-Wort, lamotrigine, Topiramate, quetiapine, cyclosporin, hepatic enzyme-inducing drugs (e.g., phenytoin, carbamazepine phenobarbital, primidone, rifampin), enzyme inhibitors (e.g., felbamate), aspirin, cimetidine, erythromycin, carbapenem (e.g., Panipenem, Aztreonam, Imipenem, Meropenem), diazepam, ethosuximide, lamotrigine, phenytoin, nimodipine